Thunderstorms will approach the region this evening from the west in advance of a disturbance and low pressure center that tracks through the region tonight and early Saturday. Tonight and Saturday offer the opportunity for more rain and thunder, with tonight through very early Saturday the best chance for the most widespread shower and thunderstorm activity in the region.
Computer modeling suggests we should be dry in the city through dinner, with storms approaching the western suburbs after 7 PM per higher resolution modeling. There is a slight chance of some gusty winds and some hail with these storms as they track through Central and Eastern Pennsylvania. These storms will weaken somewhat as they reach Philadelphia but the region should get at least some rain late this evening.
The bulk of the precipitation with this disturbance falls late tonight and overnight, with showers lingering in spots into Saturday morning. However, Saturday does not appear to be a total washout. There will be a lull in the shower activity from mid/late morning into the afternoon hours before a second round of showers and storms potentially fires up. It wouldn't shock us to see some sunshine in the midday hours around town...that will do just enough to agitate the atmosphere to fire up more thunderstorm activity in advance of a cold front that will cross the region Saturday night.
Rainfall amounts will be scattered between a quarter inch and three-quarters of an inch (perhaps more than that), with the tendency for less rain south of the city and more rain northwest. Tonight's thunderstorm activity will be a bit more prevalent to the city's northwest, with tomorrow's scatterings of showers and storms showing no real geographic tendency.